It is common to have diarrhea and pain after GB surgery. The left lower pain is not usually from the GB, but probably from your previous surgery, could even be scar tissue providing there is no swelling or fever associated with the pain. It is important to follow a low fat diet, eat small balanced meals, instead of 2-3 meals, separate them into 4-6 small meals. You should try to eliminate caffeine, chocolate, sugary foods, and acids such as citrus fruits and tomato/tomatoe sauce. After a while you may be able to tolerate some of these. Start adding fiber SLOWLY everyday, there are many types such as pills, wafers or powders, see what one is most convenient for you. Drink adequate amount of water, try camomille tea. (spelling?)
Also, probiotics are very good for everyone. Probiotics can be found in nofat yogurts, kefir and in pill form. Stay away from the dairy products if they seem to give you diarrhea, if this is a problem, you should make sure you are getting Calcium, vit D in another form. Make sure that the bacillus and other cultures in the probiotics are guarenteed to be "active" and in the amount listed. These are the good bacteria that we need to be healthy.
Don't forget that it is very important to exercise everyday, even if it is a short brisk walk, slow deep breathing.
A reputable health food store or a pharmacist should be able to help you. Hope you feel better soon.
Sadiemae, a lot of people unfortunately have diarrhea following GB surgery. It's typically due to the fact that you may be unable to process fats the way you did before the surgery. In addition to trying some fiber and probiotics (as long as you don't have any indications of pancreatic dysfunction or immunosuppression), try following a low fat diet. For many that can make a big difference.